Equivalent fractions

This task is about working with equivalent fractions.
a)   i)   Which fraction is not equivalent to \(1 \over 4\)?
             (A)   \(4 \over 16\)
             (B)   \(8 \over 32\)
             (C)   \(12 \over 64\)
             (D)   \(32 \over 128\)
 
       ii)   Which fraction is not equivalent to \(15 \over 45\)?
             (A)   \(6 \over 18\)
             (B)   \(8 \over 27\)
             (C)   \(12 \over 36\)
             (D)   \(18 \over 54\)

b)   Write these fractions in their simplest form.
 
  i) \(3 \over 15\)  = ​ ​
  ii) \(18 \over 24\)  = ​ ​
  iii) \(15 \over 21\)  =